Mechanical Philosophy, 65 



^discovered, and received ample illustration. The 

 learned and indefatigable labours of Father Bosco- 

 vicH, and of M. De la Place, for determining 

 the orbits of comets, have been long known and 

 praised by astronomers. The great works of M. 

 P NGRE^ and of Sir Henry Englefield, on this 

 brancih of astronomical philosophy, are entitled to a 

 place among the most full and useful of those 

 Vvhich have appeared on the subject.* But besides 

 what has been effected by the useful inquiries of 

 these gentlemen, the observations of many others, 

 and particularly of De Lalande, and his country- 

 men. Messier, and Mechain, and also of Burck- 

 HARDT, an illustrious German astronomer, have 

 contributed much to extend our knowledge of 

 comets. It is further worthy of remark, that the 

 difficulty of making observations on comets has 

 been, within a few years, greatly diminished. 

 The methods of calculating their elements ate now 

 short and easy, in comparison with what they 

 were half a century ago. Operations which then 

 occupied many days, may now be dispatched with 

 accuracy, in a few hours. 



The importance of accurate observations on the 

 ^fixed stars, in order to ascertain their motion^ 

 places, and relative circumstances, is known to 

 every astronomer. It is to the stars we are 

 obliged to refer all the motions of the sun^ the 

 planets, and the comets. In this part of the sci- 

 ence under consideration, much has been done 

 during the last century. The catalogue of stars 



iiave made it questionable whether the doctrine long entertained, and consi- 

 dered as settled by him and other astronomers, that comets revolve, be not 

 erroneous. This doubt will probably soon receive a solution, if the spirit 

 of zeal and industry should continue which at present animates many Eu- 

 ropean philosophers. 



b Treatise on Comets^ by M. PiNGRE, a vols. 4to. Paris, 1783. Th& 

 Determination of the Orbits of Comets^ according to the Methods of Father Bos- 

 covicH, and M. T>i. la Place, ivitb new and eoTn^lett tablti^ by SijP 

 Henry E.nglefield, 410. 1799. 



K 



